Currently, all electrical accessories for flush mounting are similar in structure.
Such an electrical accessory thus comprises: an electrical box that is open at the front and that is for fitting through an opening formed in the hollow partition; an accessory support in the form of a frame for fitting on the open front face of the electrical box; an accessory mechanism (e.g. a power-outlet or a switch mechanism) for blocking in the opening defined by the accessory support; and a finishing plate for fastening on the accessory support so that it hides said accessory support and so that it borders the accessory mechanism in attractive manner.
In particular, the accessory mechanism comprises an insulating block that houses connection terminals for connecting to the local electricity network, and that is closed at the front by a piece of trim that is user-accessible (a toggle or push button for an on/off switch or two-way switch, a connection well for a power outlet, . . . ).
The insulating block is generally snap-fastened in permanent manner in the accessory support, whereas the accessory support is fastened to the electrical box by means of screws, having heads that bear against the accessory support and having threaded shanks that are screw-fastened in corresponding screw-fastener wells provided in the electrical box.
Consequently, when the user wishes to replace the accessory mechanism with an improved mechanism, the user is forced to unscrew the screws that hold the accessory support on the electrical box, to remove the accessory support, to disconnect the mechanism carried by the support from the electric wires coming from the local electricity network, to replace the support and the mechanism with another accessory support carrying the new accessory mechanism, to reconnect the new mechanism, and then to tighten the screws, and this turns out to be tricky.
In order to install such an electrical accessory in an opening formed in a hollow partition, it is likewise necessary to implement a large number of operations.
It is thus necessary to pull at least one cable-routing conduit through the opening formed in the hollow partition, to engage the end of each conduit in the electrical box, to fasten the electrical box in the opening formed in the hollow partition, pushing each conduit back into the hollow partition, to screw-fasten the accessory support on the electrical box, taking care to place it vertically, to connect the electric wires coming from each conduit to the terminals of the accessory mechanism, to block the accessory mechanism in the accessory support, and to fit the finishing plate on the accessory support.
These operations are time-consuming and tricky to perform.
The number of elements necessary for fastening the electrical accessory on the hollow partition is also large, and this is costly.
Document DE 9 106 123 discloses an electrical accessory that is easier and quicker to assemble.
That electrical accessory includes an accessory mechanism for engaging in an electrical box having a side wall that presents two diametrally-opposite slots.
As described in that document, the accessory mechanism comprises a base and two opposite side tabs that extend from the rear wall of the base towards the front, and that carry snap-fastener teeth that are adapted to catch onto the slots of the electrical box. More precisely, the snap-fastener teeth are designed to pass through the slots and to catch onto the wall panel. In other words, the snap-fastener teeth make it possible not only to hold the accessory mechanism in the electrical box, but also to block the electrical box in the wall panel.
In addition, in that document, provision is made to use a finishing plate that is fastened to the edge of the electrical box, and that co-operates with the front ends of the side tabs so as to lock the side tabs in the slots of the side wall of the electrical box, so as to avoid them separating from the slots.
The major drawback of that electrical accessory is that it requires cavities to be formed in the wall panel for receiving the snap-fastener teeth of the accessory mechanism.
In practice, it turns out to be very difficult to form such cavities in the wall panel. Furthermore, when the wall panel is made of plaster (which might crumble), that type of fastening is not robust enough with regard to standards in force.
The dimensions of the cavities formed in the wall panel must also be adjusted very precisely (as a function of the dimensions of the side tabs of the mechanism). In practice, such a degree of accuracy is difficult to achieve when the cavities are hollowed out in the wall panel by means of tools.
In other words, there is a high risk that either the assembly cannot be mounted on the wall, or it presents very large clearance once mounted on the wall.
Another drawback is that the dimensions of the side tabs (in particular the positions of the snap-fastener teeth and of the front ends of the side tabs) must be adjusted very accurately so that they can guarantee their function of blocking the mechanism towards the front (by the snap-fastener teeth) and towards the rear (by the front ends of the flexible tabs), and so that they can guarantee their function of blocking the box in the wall. In practice, such a degree of accuracy is difficult to achieve for a mechanism that is intended to be mass produced.
In addition, although it is stated in that document that the assembly may be removed by removing the finishing plate, then by using a screw-driver to act on the front ends of the side tabs, via the sides of the mechanism, so as to cause the side tabs to flex, it nevertheless remains that such removal turns out to be tricky and requires the use of a tool.
Finally, the use of a finishing plate for fastening to the front edge of the electrical box turns out to be very troublesome in practice. Specifically, after the electrical box has been engaged in the wall panel, it often happens that said wall panel is covered with a covering (wallpaper, plaster, . . . ), such that the front edge of the electrical box is no longer accessible, and such that it is no longer possible to fasten the finishing plate thereto.